PSI - Issue 62

M. Domaneschi et al. / Procedia Structural Integrity 62 (2024) 1028–1035 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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concrete creep, steel tendon corrosion, and more, causing excessive vertical deflections in cantilever ends, have been reported since the 90s ( Bažant and Chern 1984; Bažant and Kim 1991; Bažant and Panula 1980). Instances of bridge deterioration and even partial collapse (Lu et al. 2017) stem from these issues, aggravated by increased traffic loads (Morgese et al. 2020) and potential construction problems (Lucko and De La Garza 2003). Despite efforts by multiple researchers (Gu et al. 2011; Wang and Fu 2015; Domaneschi et al. 2020), a comprehensive mechanism to calculate and predict these faults is lacking. The absence of a standard solution led the authors to propose an alternative approach, diverging from traditional on-site inspections and extensive sampling. This paper offers an option for assessing fragile assets with uncertain structural integrity, where destructive testing or extensive sample collection is impractical. Leveraging digitalization and monitoring trends in the construction sector toward infrastructure resilience (Argyroudis et al. 2022), the suggested solution relies on computer analysis and innovative tools like drone-based photogrammetry (Varbla et al. 2021), prioritizing cost-effectiveness and eco-friendliness. Laser scanning technology's growing popularity (Lõhmus et al. 2018) and ability to provide detailed results in limited time frames (Witcher 2017) further supports this proposal. Moreover, this study is also intended to be complementary to a previous study that focused on the impact of different retrofit solutions for this type of bridge, particularly in terms of environmental sustainability and cost. So it went to evaluate the different retrofit solutions by quantifying their resilience (Mitoulis et al. 2023). The case study of the Polyfytos Bridge in Western Macedonia, Greece, has been selected for the development of this multi-step study. 1.1. The structure and traditional inspections The Polyfytos bridge, constructed in 1975 in the Municipality of Western Macedonia, Kozani, Greece, spans the artificial Polyfytos lake, serving as a critical link in both local and national road networks. A segment of the bridge, extending 260 meters from piers 22, 23, and 24 (Fig.1), was constructed using the balanced cantilever method, contributing to the bridge's total length of 1372 meters. Recent inspections, conducted by multiple inspectors including one of this paper's authors, highlighted excessive deflections at the cantilevers' free ends, a common issue in aging balanced cantilever bridges (Markogiannaki et al. 2022). Preliminary assessments identified corrosion and local concrete damage, raising substantial concerns about the bridge's structural integrity. Consequently, traffic restrictions were implemented, including weight limitations for heavy vehicles and reduced speed limits to mitigate dynamic impacts. Typically, extensive sampling, destructive testing, and vibration/loading checks are employed to assess material conditions. However, due to concerns regarding the deck's capacity at critical points, these methods weren't authorized by the owners (Markogiannaki et al. 2022). Moreover, due to the bridge's significance in the busy national road network (part of the E65 Central Greece Highway), conducting tests that could disrupt traffic poses significant challenges. 1.2. The “digital” approach to inspection In response, a digitalized damage assessment approach is proposed, utilizing advanced computational tools applicable to various structural assets. While various monitoring systems using sensor technology have been suggested (Li et al. 2022; Zhou et al. 2021), none have achieved universal optimality due to varying accuracy levels. Our innovative approach minimizes intrusion, time, cost, and environmental impact. The proposed procedure begins with a fault report, determining the need for on-site inspections. High-tech surveying tools, such as drone-based photogrammetry, offer valuable data on deflections, rotations, and visible cracks without physical access to the structure (Li et al. 2022). These measurements create deflection curves for mathematical comparison with other data sets. Additionally, information from design reports and literature supplements this analysis, contributing to an advanced structural model. Given existing knowledge gaps ( Bažant and Jirásek 2018), an advanced model considers potential causes like creep and shrinkage observed in similar structures. Scenario-based analyses explore various parameters' effects on the structure. Comparing these scenarios' deflection curves to measured results identifies potential causes, guiding further investigation without providing absolute conclusions.